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Winter Measurements of Heavy-duty Vehicles to Characterize the Cold Temperature Effectiveness of Selective Catalytic Reductions Catalyst in Controlling Oxide of Nitrogen Emissions

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  • Principal Investigators: Gary Bishop (University of Denver)
  • Study Period: July 1, 2020, – June 30, 2021
  • Funded by Science for Solutions Research Grant: $52,000
  • DAQ Contact: Joe Thomas (joethomas@utah.gov)

The Salt Lake City region in Utah experiences periods of high particulate levels in the winter months due to the combination of its topography, winter atmospheric inversions and local emissions. Secondary nitrate particles comprise the dominant fraction of the particles in these episodes and are the result of the reaction of oxides of nitrogen with ammonia. Recent research has shown that peak wintertime PM2.5 concentration maxima have not been reduced along with the summertime maxima NOx indicating a possible difference in the winter inventories. One possible explanation for these differences is that the NOx emissions inventory is underestimated during the winter months. In addition, work in Europe on light-duty diesel vehicles has shown a significant temperature dependence in NOx emissions with emissions increasing with decreasing temperature.

A significant fraction of NOx emissions in the Salt Lake City area are produced by heavy-duty vehicles operating in or traveling through the area on the interstate highway system. New technology in the form of selective catalytic reduction catalysis to control NOx tailpipe emissions have been entering the heavy-duty fleet since 2011 and winter-time performance of these systems have received little attention. Because of the importance of winter-time NOx emission factors from heavy-duty vehicles to the Salt Lake City NOx inventory we are proposing to conduct a winter-time measurement campaign to measure them.

Using the University of Denver’s (DU) remote vehicle exhaust sensor we propose to measure heavy-duty vehicle emission factors for carbon monoxide, hydrocarbon, nitric oxide, nitrogen dioxide and ammonia from in-use vehicles in the Salt Lake City area. A week of measurements at a weigh station or other location frequented by heavy-duty vehicles will produce 1000 or more measurements allowing a detailed look at the emissions distribution of the heavy-duty vehicle fleet during winter temperature conditions. This data will allow the direct emissions comparisons between similar model year vehicles to data collected in other areas of the country during warmer weather. This data set should also allow the current inventory for the Salt Lake City area to be compared to an updated version using these new wintertime emission values.

Heavy Duty Vehicles
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